1. Field of the Invention
The present invention relates to a method and apparatus for a vacuum process, and particularly, to a method and apparatus for a vacuum process of isostatic pressing of powder material.
2. Background of the Invention
Isostatic pressing is a type of pressing of powder material, and is utilized to obtain a uniform density by applying a pressure to powder material in every direction. As one example, metallic powder undergoes isostatic pressing and a sintering process to fabricate a metallic tool. As another example, ceramic powder undergoes isostatic pressing to massively fabricate each kind of electric or mechanical components.
Methods for charging a high explosive in a weapon system include a melting type for charging a high explosive in a melting manner, a casting type, a pressing type for pressing explosive raw materials with a high pressure and then processing in correspondence to a shape of the weapon system, etc. Especially, in case of the pressing type, isostatic pressing is used to fabricate powder molded body having a uniform density.
If explosive powder to be isostatic-pressed contains air remaining therein, the air is pressed in an insulated state when the explosive powder undergoes isostatic pressing. This may cause a hot spot to increase a possibility of explosion. Accordingly, the air inside the explosive powder need to be removed at a previous stage of the isostatic pressing.
In order to remove the air, a vacuum pump is connected to an inlet of a rubber bag containing explosive powder therein to perform a vacuum process. However, the inlet of the rubber bag may be sealed due to a vacuum state implemented during the vacuum process. Furthermore, while the inlet of the rubber bag is sealed, air may be introduced into the rubber bag little by little. This may cause the vacuum state inside the explosive powder to be gradually changed into a non-vacuum state. This explosive powder may cause an inferior density of a molded explosive body, thereby resulting in degradation of massive production.